Osteology everywhere: Pelvis has left the building

The vernal awakening has brought rain to Ann Arbor, and right on here on main campus I spotted the rain-splotched silhouette of an articulated human pelvis (left).

Check out those short and flaring iliac blades, and the shortness of the ischium. These features are associated with repositioning key muscles for walking and running on two feet, and are very unlike what is seen in the four-legged, suspensory climbing apes.

But just how ‘human’ are these features? The crushed pelvis of Oreopithecus bambolii, a ~8 million year old fossil ape from Italy, has somewhat human-like short ilia (left). This pelvis also has weak anterior inferior iliac spines (Rook et al. 1999), which anchor the hip/trunk flexor muscle rectus femoris, and are allegedly a developmental novelty seen only in hominids (Lovejoy et al. 2009). These traits have led some to claim that Oreopithecus was a hominid, or at least bipedal. Without getting into that debate, I’ll just say that seeing these ‘bipedal’ features in this late Miocene ape’s pelvis weakens the case that their presence in Ardipithecus ramidus indicates a unique connection between Ardi and later, true hominids like australopiths.

UPDATE: Check the comments for notes on the Ardi and Oreo fossils from someone who’s actually studied them (I myself have only seen pictures and read about them).

Rook, L. (1999). Oreopithecus was a bipedal ape after all: Evidence from the iliac cancellous architecture Proceedings of the National Academy of Sciences, 96 (15), 8795-8799 DOI: 10.1073/pnas.96.15.8795

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3 thoughts on “Osteology everywhere: Pelvis has left the building”

Hope this won't come off as too self-serving, but have a look at Jungers (JHE, 1987) on "Body size and morphometric affinities of the appendicular skeleton in Oreopithecus bambolii (IGF 11778)." The ilium of Oreo isn't short at all; its relative length is comparable to that seen in a variety of apes and Old World Monkeys (Table 2).I had the opportunity to study the Ardipithecus fossils in Addis last November. The distance between the acetabular margin and the sacroiliac joint is remarkably short, and much more human-like than in Oreo or any extant ape; i.e., the ilium really was short in Ardi. And the lateral metatarsals are those of a bipedal hominin, a weird one to be sure, but they are uniquely hominin. Other bits of the postcranium also reveal shared-derived features with later hominins. Seeing really is believing in this case.I enjoy your blog. Tx.WL Jungers